The present invention relates generally to heat exchangers and more particularly to heat exchangers of the type wherein special care must be taken that the heat exchange media utilized will not come into contact with each other. More specifically, the invention is directed toward the structure of the tube sheet assembly for such heat exchangers.
In heat exchangers which must utilize immiscible fluid heat exchange media which for certain reasons will cause severe problems if they come in contact with each other, special care must be exhibited to avoid mixing or intermingling of the heat exchange media. Otherwise, vigorous explosive reactions may occur or mixing of the media may result in serious or heavy corrosion to parts of the heat exchangers.
Accordingly, measures are usually provided to avoid leakages which will mostly occur in the region of points of joinder between various parts of the heat exchanger.
Conditions such as those suggested above exist especially in tube-reactors which perform catalytic reactions.
Additionally, the coefficient of heat transfer may be lowered because of wide spacing of tubes which may be provided for safety reasons. The wide spacing of the tubes may become uneconomical and may, in addition, have an adverse effect on space requirements because of the larger dimensions of the heat exchanger.
Furthermore, in designs of the type discussed, two tube sheets are provided which may assume different temperature levels inasmuch as an inner tube sheet may assume the temperature of the medium surrounding the tubes while the outer tube sheet may assume the temperature of the medium flowing through the tubes and, thus, approximate the temperature of the tubes. This will result in unequal heat expansion of the two tube sheets and, therefore, will cause relative transverse movement of the tubes in the tube sheet planes.
In the prior art, there are known tube sheet constructions wherein several tube sheet plates are arranged to lie immediately adjacent each other with the plates being rigidly connected with each other.
Furthermore, in attaching the tubes of the heat exchanger with the tube sheets, a rolling technique involving rolling of the tubes into the tube sheet has been utilized and as a result a rather strong but not always absolutely leak proof joint may be achieved.
A further problem may arise because of the desirability of controlling and accumulating any leakage liquid which may be produced in order to avoid further problems. Toward this end, an arrangement of grooves or ducts may be provided, with the grooves or ducts being connected with the tube sheet at a point located adjacent the exterior of each tube.
The invention is particularly directed toward providing a structure for a heat exchanger wherein problems may arise due to leakage of the fluid heat exchange media by arranging the construction of the tube sheets such that an advantageous approach may be taken with regard to any leakage that may occur.